Question

during which phase of mitosis do chromosomes line up along the middle of the cell?
a. prophase
b. metaphase
c. anaphase
d. telophase

Explanation:

To determine the phase of mitosis where chromosomes line up at the cell's middle, we analyze each option:

• Option A (Prophase): Chromosomes condense, the nuclear envelope breaks down, and spindle fibers form, but chromosomes do not line up at the middle here.
• Option B (Metaphase): In this phase, chromosomes align along the metaphase plate (the middle of the cell) due to the action of spindle fibers. This matches the described event.
• Option C (Anaphase): Sister chromatids are pulled apart to opposite poles of the cell, so chromosomes are moving away from the middle, not lining up.
• Option D (Telophase): Chromosomes de - condense, the nuclear envelope reforms, and the cell starts to divide, with no chromosome alignment at the middle.

Answer:

B. metaphase